WO2008083018A1 - Unité de lumière d'éclairage et afficheur l'utilisant - Google Patents

Unité de lumière d'éclairage et afficheur l'utilisant Download PDF

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Publication number
WO2008083018A1
WO2008083018A1 PCT/US2007/088270 US2007088270W WO2008083018A1 WO 2008083018 A1 WO2008083018 A1 WO 2008083018A1 US 2007088270 W US2007088270 W US 2007088270W WO 2008083018 A1 WO2008083018 A1 WO 2008083018A1
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WO
WIPO (PCT)
Prior art keywords
light
substrate
unit
light source
reflecting cavity
Prior art date
Application number
PCT/US2007/088270
Other languages
English (en)
Inventor
Kenneth A. Epstein
Simon Magarill
Original Assignee
3M Innovative Properties Company
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Publication date
Application filed by 3M Innovative Properties Company filed Critical 3M Innovative Properties Company
Publication of WO2008083018A1 publication Critical patent/WO2008083018A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0013—Means for improving the coupling-in of light from the light source into the light guide
    • G02B6/0015—Means for improving the coupling-in of light from the light source into the light guide provided on the surface of the light guide or in the bulk of it
    • G02B6/0018—Redirecting means on the surface of the light guide
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0066—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form characterised by the light source being coupled to the light guide
    • G02B6/0068—Arrangements of plural sources, e.g. multi-colour light sources

Definitions

  • edge-lit backlights Many such backlights fall into the categories of "edge-lit” or “direct-lit.” These categories differ in the placement of the light sources relative to the output area of the backlight, where the output area defines the viewable area of the display device.
  • edge- lit backlights one or more light sources are disposed along an outer border or edge of the backlight construction outside the zone corresponding to the output area.
  • the light sources typically emit light into a light guide, which has length and width dimensions on the order of the output area and from which light is extracted to illuminate the output area.
  • direct- lit backlights an array of light sources is disposed directly behind the output area, and a diffuser is placed in front of the light sources to provide a more uniform light output.
  • Some direct-lit backlights also incorporate an edge-mounted light, and are thus illuminated with a combination of direct-lit and edge-lit illumination.
  • a display is illuminated with light from a number of different light sources that produce light of different colors. Because the human eye more easily discerns variations in color than in brightness, it can be difficult to effectively mix light sources that produce different colors to provide white illumination light to the display. It is important in these situations that the light from the different light sources be mixed so that the color, as well as the brightness, are uniform across the displayed image. Summary
  • the present disclosures provides an illumination light unit that includes a substrate, and at least a first light source positioned proximate the substrate.
  • the first light source is capable of producing illumination light generally along an illumination axis that is substantially orthogonal to the substrate.
  • the illumination light unit also includes an elongated reflecting cavity including a curved reflector that is concave down facing the substrate.
  • the curved reflector includes an elliptical cross- section in a plane substantially orthogonal to the substrate.
  • the first light source is positioned proximate a first line focus of the reflecting cavity and an output surface of the reflecting cavity is positioned proximate a second line focus of the reflecting cavity.
  • the present disclosure provides a display that includes an image- forming panel having an illumination side, and a backlight unit disposed to the illumination side of the image-forming panel.
  • the backlight unit includes a light guide including a first input surface and at least one illumination light unit including an output surface. The output surface is positioned proximate the first input surface of the light guide.
  • the illumination light unit includes a substrate, and at least a first light source positioned proximate the substrate. The first light source is capable of producing illumination light generally along an illumination axis that is substantially orthogonal to the substrate.
  • the illumination light unit also includes an elongated reflecting cavity including a curved reflector that is concave down facing the substrate.
  • the curved reflector includes an elliptical cross-section in a plane substantially orthogonal to the substrate.
  • the first light source is positioned proximate a first line focus of the reflecting cavity and the output surface of the reflecting cavity is positioned proximate a second line focus of the reflecting cavity.
  • the present disclosure provides a backlight that includes a light guide including a first input surface, and at least one illumination light unit including an output surface positioned proximate a first input surface of the light guide.
  • the illumination light unit further includes a substrate, and at least a first light source positioned proximate the substrate.
  • the first light source is capable of producing illumination light generally along an illumination axis that is substantially orthogonal to the substrate.
  • the illumination light unit further includes an elongated reflecting cavity including a curved reflector that is concave down facing the substrate.
  • the curved reflector includes an elliptical cross-section in a plane substantially orthogonal to the substrate.
  • the first light source is positioned proximate a first line focus of the reflecting cavity and the output surface of the reflecting cavity is positioned proximate a second line focus of the reflecting cavity.
  • FIG. 1 is a schematic cross-section view of one embodiment of an edge-lit liquid crystal display system.
  • FIGS. 2A-B are schematic cross-section views of one embodiment of a backlight that includes an illumination light unit and a light guide.
  • FIG. 3 is a schematic cross-section view of one embodiment of a reflecting cavity having a curved reflector with an elliptical cross-sectional shape.
  • FIG. 4 is a schematic cross-sectional view of another embodiment of a backlight that includes an illumination light unit and a light guide.
  • FIG. 5 is a schematic cross-section view of an embodiment of a backlight that includes two illumination light units proximate an input surface of a light guide.
  • the present disclosure is applicable to illuminated signs and displays, such as liquid crystal displays (LCDs, or LC displays), and is also applicable to displays that are illuminated using light sources positioned to the side of the display panel, known as edge- lit displays.
  • the disclosure is believed to be particularly useful for displays that are illuminated by light sources of different colors.
  • the disclosure is believed also to be applicable to systems that provide space lighting.
  • the present disclosure provides an illumination light unit that includes an elongated reflecting cavity having a curved reflector.
  • the curved reflector has an elliptical cross-section that forms a first line focus and a second line focus.
  • One or more light sources can be placed proximate the first line focus such that light produced by the light sources is directed by the curved reflector to the second line focus.
  • the elongated reflecting cavity also includes an output surface that is positioned proximate the second line focus.
  • the one or more light sources include sources that produce different wavelengths of light, such light is allowed to expand within the cavity in a direction substantially parallel to the first and second line focuses such that the various wavelengths can be mixed, thereby providing uniform white light to a display, sign, etc.
  • the output surface of the illumination light unit can be positioned proximate an input surface of a light guide to provide a backlight, e.g., for displays, signs, etc.
  • the second line focus is positioned proximate the input surface of the light guide. Because a substantial portion of the light emitted by the light sources is directed by the curved reflector to the second line focus, this substantial portion of the light is directed into the light guide. Further, placing the input surface of the light guide at the second line focus allows for thin light guides because the light being transmitted through the output surface should include its narrowest profile in the thickness direction of the light guide. In other words, positioning the input surface at the second line focus allows the light guide to capture nearly all of the light emitted by the illumination light unit.
  • FIG. 1 illustrates one embodiment of an edge-lit display 100 that includes a backlight 112 including illumination light units 120.
  • a display 100 can be used, for example, in an LCD monitor or LCD-TV.
  • the display 100 uses a liquid crystal (LC) image-forming panel 150, which typically includes a layer of LC 152 disposed between panel plates 154.
  • the plates 154 are often formed of glass, and may include electrode structures and alignment layers on their inner surfaces for controlling the orientation of the liquid crystals in the LC layer 152.
  • the electrode structures are commonly arranged so as to define LC panel pixels, i.e., areas of the LC layer 152 where the orientation of the liquid crystals can be controlled independently of adjacent pixels.
  • a color filter may also be included with one or more of the plates 154 for imposing color on the displayed image.
  • An upper absorbing polarizer 156 is positioned above the LC layer 152 and a lower absorbing polarizer 160 is positioned below the LC layer 152. In the illustrated embodiment, the upper and lower absorbing polarizers 156, 160 are located outside the display panel 150. The absorbing polarizers 156, 160 and the display panel 150, in combination, control the transmission of light from a backlight 112 through the display panel 150 to the viewer.
  • a pixel of the LC layer 152 when a pixel of the LC layer 152 is not activated, it does not change the polarization of light passing therethrough. Accordingly, light that passes through the lower absorbing polarizer 160 is absorbed by the upper absorbing polarizer 156, when the absorbing polarizers 156, 160 are aligned perpendicularly. When the pixel is activated, the polarization of the light passing therethrough is rotated, so that at least some of the light that is transmitted through the lower absorbing polarizer 160 is also transmitted through the upper absorbing polarizer 156.
  • the controller 180 may include, for example, a computer or a television controller that receives and displays television images.
  • One or more optional layers 158 may be provided over the upper absorbing polarizer 156, for example, to provide mechanical and/or environmental protection to the display surface.
  • the layer 158 may include a hardcoat over the absorbing polarizer 156.
  • LC displays may operate in a manner different from that described herein and, therefore, differ in detail from the described system.
  • the absorbing polarizers may be aligned parallel and the LC panel may rotate the polarization of the light when in an unactivated state. Regardless, the basic structure of such displays remains similar to that described herein.
  • the backlight 112 includes a light guide 130 and one or more illumination light units 120 that produce the illumination light and direct the illumination light into the light guide 130.
  • the illumination light units 120 include one or more light sources 124 to produce the illumination light.
  • the light sources 124 are shown schematically. In most cases, these sources 124 are compact light emitting diodes (LEDs). In this regard, “LED” refers to a diode that emits light, whether visible, ultraviolet, or infrared. It includes incoherent encased or encapsulated semiconductor devices marketed as "LEDs,” whether of the conventional or super radiant variety.
  • the LED emits non- visible light such as ultraviolet light, and in some cases where it emits visible light, it is packaged to include a phosphor (or it may illuminate a remotely disposed phosphor) to convert short wavelength light to longer wavelength visible light, in some cases yielding a device that emits white light.
  • An "LED die” is an LED in its most basic form, i.e., in the form of an individual component or chip made by semiconductor processing procedures. The component or chip can include electrical contacts suitable for application of power to energize the device. The individual layers and other functional elements of the component or chip are typically formed on the wafer scale, and the finished wafer can then be diced into individual piece parts to yield a multiplicity of LED dies.
  • CCFLs linear cold cathode fluorescent lamps
  • HCFLs hot cathode fluorescent lamps
  • CCFL/LED cool white and warm white
  • CCFL/HCFL cool white and warm white
  • the combinations of light emitters may vary widely, and include LEDs and CCFLs, and pluralities such as, for example, multiple CCFLs, multiple CCFLs of different colors, and LEDs and CCFLs.
  • a linear surface emitting light guide emitting light along its length and coupled to a remote active component (such as an LED die or halogen bulb), and to do likewise with other rows of sources.
  • a remote active component such as an LED die or halogen bulb
  • Examples of such linear surface emitting light guides are disclosed in U.S. Patent Nos. 5,845,038 (Lundin et al.) and 6,367,941 (Lea et al).
  • Fiber-coupled laser diode and other semiconductor emitters are also known, and in those cases the output end of the fiber optic waveguide can be considered to be a light source with respect to its placement in the disclosed illumination light units.
  • passive optical components having small emitting areas such as lenses, deflectors, narrow light guides, and the like that give off light received from an active component such as a bulb or LED die.
  • an active component such as a bulb or LED die.
  • a passive component is a molded encapsulant or lens of a side-emitting packaged LED.
  • the backlight 112 continuously emits white light
  • the image-forming panel 150 is combined with a color filter matrix to form groups of multicolored pixels (such as yellow/blue (YB) pixels, red/green/blue (RGB) pixels, red/green/blue/white (RGBW) pixels, red/yellow/green/blue (RYGB) pixels, red/yellow/green/cyan/blue (RYGCB) pixels, or the like) so that the displayed image is polychromatic.
  • YB yellow/blue
  • RGB red/green/blue
  • RGBW red/green/blue/white
  • RYGB red/yellow/green/blue
  • RYGCB red/yellow/green/cyan/blue
  • polychromatic images can be displayed using color sequential techniques, where, instead of continuously back-illuminating the panel 150 with white light and modulating groups of multicolored pixels in the panel 150 to produce color, separate differently colored light sources within the backlight 112 itself (selected, for example, from red, orange, amber, yellow, green, cyan, blue (including royal blue), and white in combinations such as those mentioned above) are modulated such that the backlight flashes a spatially uniform colored light output (such as, for example, red, then green, then blue) in rapid repeating succession.
  • a spatially uniform colored light output such as, for example, red, then green, then blue
  • This color-modulated backlight is then combined with a display module that has only one pixel array (without any color filter matrix), the pixel array being modulated synchronously with the backlight to produce the whole gamut of achievable colors (given the light sources used in the backlight) over the entire pixel array, provided the modulation is fast enough to yield temporal color-mixing in the visual system of the observer.
  • Examples of color sequential displays also known as field sequential displays, are described in U.S. Patent No. 5,337,068 (Stewart et al.) and U.S. Patent No. 6,762,743 (Yoshihara et al.).
  • the backlight 112 can include filters or specific sources that emit predominantly in one visible wavelength or color.
  • the illumination light unit 120 may include an elongated reflecting cavity 120 that is used to collect and direct light from the light sources 124 to the light guide 130.
  • the light guide 130 guides illumination light from the light sources 124 to an area behind the panel 150, and directs the light to the panel 150.
  • the light guide 130 may receive illumination light through a single edge, or through multiple edges. In other embodiments, not illustrated, the light may be coupled into the light guide 130 through a light coupling mechanism other than the edge of the light guide 130.
  • a base reflector 114 may be positioned on the other side of the light guide 130 from the display panel 150.
  • the light guide 130 may include light extraction features 132 that are used to extract the light from the light guide 130 for illuminating the display panel 150.
  • the light extraction features 132 may include diffusing spots on the surface of the light guide 130 that direct light either directly towards the display panel 150 or towards the base reflector 114. Other approaches may be used to extract the light from the light guide 130.
  • the base reflector 114 is preferably highly reflective for enhanced panel efficiency.
  • the base reflector 114 may have an average reflectivity for visible light emitted by the light sources of at least 90%, 95%, 98%, 99%, or more.
  • the base reflector 114 can be a predominantly specular, diffuse, or combination specular/diffuse reflector, whether spatially uniform or patterned.
  • the base reflector 114 can be made from a stiff metal substrate with a high reflectivity coating, or a high reflectivity film laminated to a supporting substrate.
  • Suitable high reflectivity materials include VikuitiTM Enhanced Specular Reflector (ESR) multilayer polymeric film available from 3M Company; a film made by laminating a barium sulfate-loaded polyethylene terephthalate film (2 mils thick) to VikuitiTM ESR film using a 0.4 mil thick isooctylacrylate acrylic acid pressure sensitive adhesive, the resulting laminate film referred to herein as "EDR II” film; E-60 series LumirrorTM polyester film available from Toray Industries, Inc.; porous polytetrafluoroethylene (PTFE) films, such as those available from W. L.
  • ESR VikuitiTM Enhanced Specular Reflector
  • the base reflector 114 may be substantially flat and smooth, or it may have a structured surface associated with it to enhance light scattering or mixing. Such a structured surface can be imparted (a) on the reflective surface of the base reflector 114, or (b) on a transparent coating applied to the reflective surface.
  • a highly reflecting film may be laminated to a substrate in which a structured surface was previously formed, or a highly reflecting film may be laminated to a flat substrate (such as a thin metal sheet, as with VikuitiTM Durable Enhanced Specular Reflector-Metal (DESR- M) reflector available from 3M Company) followed by forming the structured surface, such as with a stamping operation.
  • a structured surface can be imparted (a) on the reflective surface of the base reflector 114, or (b) on a transparent coating applied to the reflective surface.
  • a highly reflecting film may be laminated to a substrate in which a structured surface was previously formed, or a highly reflecting film may be laminated to a flat substrate (such as
  • a transparent film having a structured surface can be laminated to a flat reflective surface, or a transparent film can be applied to the reflector and then afterwards a structured surface imparted to the top of the transparent film.
  • the backlight 112 can also include sides and ends (not shown) located along the outer boundary of the backlight 112 along edges that do not include an illumination light unit. Such sides are preferably lined or otherwise provided with high reflectivity vertical walls to reduce light loss and improve recycling efficiency.
  • the same reflective material used for the base reflector 114 can be used to form these walls, or a different reflective material can be used.
  • the side walls are diffusely reflective.
  • An arrangement 170 of light management films which may also be referred to as a light management unit, is positioned between the backlight 112 and the image-forming panel 150.
  • the light management films 170 affect the illumination light propagating from the backlight 112 so as to improve the operation of the display system 100.
  • the arrangement 170 of light management films may include a diffuser 172.
  • the diffuser 172 is used to diffuse the light received from the light sources 124, which results in increased uniformity of the illumination light incident on the panel 150. Consequently, this results in an image perceived by the viewer to be more uniformly bright.
  • the diffuser layer 172 may be any suitable diffuser film or plate.
  • the diffuser layer 172 can include any suitable diffusing material or materials.
  • the diffuser layer 172 may include a polymeric matrix of polymethyl methacrylate (PMMA) with a variety of dispersed phases that include glass, polystyrene beads, and CaCO 3 particles.
  • PMMA polymethyl methacrylate
  • Exemplary diffusers can include 3MTM ScotchcalTM Diffuser Film, types 3635-30 and 3635-70, available from 3M Company, St. Paul, Minnesota.
  • the light management unit 170 may also include a reflective polarizer 174.
  • the light sources 124 typically produce unpolarized light, but the lower absorbing polarizer 160 only transmits a single polarization state; therefore, about half of the light generated by the light sources 124 is not transmitted through to the LC layer 152.
  • the reflective polarizer 174 may be used to reflect the light that would otherwise be absorbed in the lower absorbing polarizer 160. Consequently, this light may be recycled by reflection between the reflective polarizer 174 and the reflective substrate 102.
  • At least some of the light reflected by the reflective polarizer 174 may be depolarized and subsequently returned to the reflective polarizer 174 in a polarization state that is transmitted through the reflective polarizer 174 and the lower absorbing polarizer 160 to the LC layer 152.
  • the reflective polarizer 174 may be used to increase the fraction of light emitted by the light sources 124 that reaches the LC layer 152, thereby providing a brighter display output.
  • any suitable type of reflective polarizer may be used for the reflective polarizer 174, e.g., multilayer optical film (MOF) reflective polarizers, diffusely reflective polarizing film (DRPF), such as continuous/disperse phase polarizers, wire grid reflective polarizers, or cholesteric reflective polarizers.
  • MOF multilayer optical film
  • DRPF diffusely reflective polarizing film
  • continuous/disperse phase polarizers such as continuous/disperse phase polarizers, wire grid reflective polarizers, or cholesteric reflective polarizers.
  • MOF and continuous/disperse phase reflective polarizers rely on the difference in refractive index between at least two materials, usually polymeric materials, to selectively reflect light of one polarization state while transmitting light in an orthogonal polarization state.
  • Some examples of MOF reflective polarizers are described in co-owned U.S. Patent Nos. 5,882,774 (Jonza et al.).
  • Commercially available examples of MOF reflective polarizers include VikuitiTM DBEF-D200 and DBEF-D440 multilayer reflective polarizers that include diffusive surfaces, available from 3M Company.
  • Other suitable types of DRPF are described in U.S. Patent No. 5,751,388 (Larson).
  • Wire grid polarizers are commercially available from, inter alia, Moxtek Inc., Orem, Utah.
  • cholesteric polarizers useful in connection with the present disclosure include those described, e.g., in U.S. Patent No. 5,793,456 (Broer et al.), and U.S. Patent Publication No. 2002/0159019 (Pokorny et al.). Cholesteric polarizers are often provided along with a quarter wave retarding layer on the output side so that the light transmitted through the cholesteric polarizer is converted to linearly polarized light. In some embodiments, a polarization control layer 178 may be provided between the diffuser 172 and the reflective polarizer 174.
  • Examples of polarization control layers include a quarter wave retarding layer and a polarization rotating layer such as a liquid crystal polarization rotating layer.
  • the polarization control layer 178 may be used to change the polarization of light that is reflected from the reflective polarizer 174 so that an increased fraction of the recycled light is transmitted through the reflective polarizer 174.
  • the arrangement 170 of light management films may also include one or more brightness enhancing layers.
  • a brightness enhancing layer is one that includes a surface structure that redirects off-axis light in a direction closer to the axis of the display. This increases the amount of light propagating on-axis through the LC layer 152, thus increasing the brightness of the image seen by the viewer.
  • a brightness enhancing layer is a prismatic brightness enhancing layer, which has a number of prismatic ridges that redirect the illumination light through refraction and reflection.
  • prismatic brightness enhancing layers that may be used in the display 100 include the VikuitiTM BEF II and BEF III family of prismatic films available from 3M Company, including BEF II 90/24, BEF II 90/50, BEF HIM 90/50, and BEF HIT.
  • the exemplary embodiment illustrated in FIG. 1 shows a first brightness enhancing layer 176a disposed between the reflective polarizer 174 and the image-forming panel 150.
  • a prismatic brightness enhancing layer typically provides optical gain in one dimension.
  • An optional second brightness enhancing layer 176b may also be included in the arrangement 170 of light management layers, having its prismatic structure oriented orthogonally to the prismatic structure of the first brightness enhancing layer 176a.
  • Such a configuration provides an increase in the optical gain of the display 100 in two dimensions.
  • the brightness enhancing layers 176a, 176b may be positioned between the backlight 112 and the reflective polarizer 174.
  • the different layers in the light management unit 170 may be free standing.
  • two or more of the layers in the light management unit 170 may be laminated together, for example as discussed in co-owned U.S. Patent Application Publication No. 2006/0082698 (Ko et al.).
  • the light management unit 170 may include two subassemblies separated by a gap, for example, as described in co-owned U.S. Patent Application Publication No. 2006/0082700 (Gehlsen et al.).
  • FIGS. 2A-B One embodiment of a backlight 200 that may be used with a display (e.g., display 100 of FIG. 1) is illustrated in FIGS. 2A-B.
  • Backlight 200 includes an illumination light unit 210 that includes an output surface 220, and a light guide 230 that includes a first input surface 232.
  • the output surface 220 of the illumination light unit 210 is positioned proximate the first input surface 232 of the light guide 230.
  • the backlight 200 can include two or more illumination light units positioned along the same or other edges of the light guide 230.
  • the illumination light unit 210 includes a substrate 218 and one or more light sources 216 positioned proximate the substrate 218. Each light source 216 is capable of producing illumination light generally along an illumination axis 217 that is substantially orthogonal to the substrate 218.
  • the unit 210 further includes an elongated reflecting cavity 212 that includes a curved reflector 214 that is concave down facing the substrate 218.
  • the substrate 218 may be any suitable material or materials.
  • the substrate 218 may be reflective for reflecting light from the light sources 216 propagating in a direction toward the substrate 218.
  • the reflective substrate 218 may have an average reflectivity for visible light emitted by the light sources 216 of at least 90%, 95%, 98%, 99%, or more.
  • the reflective substrate 218 can be a predominantly specular, diffuse, or combination specular/diffuse reflector, whether spatially uniform or patterned.
  • the reflective substrate 218 can be made from a stiff metal substrate with a high reflectivity coating, or a high reflectivity film laminated to a supporting substrate.
  • Suitable high reflectivity materials include VikuitiTM Enhanced Specular Reflector (ESR) multilayer polymeric film available from 3M Company; a film made by laminating a barium sulfate-loaded polyethylene terephthalate film (2 mils thick) to VikuitiTM ESR film using a 0.4 mil thick isooctylacrylate acrylic acid pressure sensitive adhesive, the resulting laminate film referred to herein as "EDR II" film; E-60 series LumirrorTM polyester film available from Toray Industries, Inc.; porous polytetrafluoroethylene (PTFE) films, such as those available from W. L. Gore & Associates, Inc.; SpectralonTM reflectance material available from Labsphere, Inc.; MiroTM anodized aluminum films (including MiroTM 2 film) available from Alanod Aluminum-
  • ESR VikuitiTM Enhanced Specular Reflector
  • the reflective substrate 218 may be substantially flat and smooth, or it may have a structured surface associated with it to enhance light scattering or mixing.
  • a structured surface can be imparted (a) on the reflective surface of the substrate 218, or (b) on a transparent coating applied to the reflective surface.
  • a highly reflecting film may be laminated to a substrate in which a structured surface was previously formed, or a highly reflecting film may be laminated to a flat substrate (such as a thin metal sheet, as with VikuitiTM Durable Enhanced Specular Reflector-Metal (DESR- M) reflector available from 3M Company) followed by forming the structured surface, such as with a stamping operation.
  • a transparent film having a structured surface can be laminated to a flat reflective surface, or a transparent film can be applied to the reflector and then afterwards a structured surface imparted to the top of the transparent film.
  • the light sources 216 may be positioned proximate the substrate 218 such that the light sources 216 are on, embedded in, or below the substrate 218.
  • the light sources 216 and conductors for providing current to the light sources 216 may be positioned on the substrate 218.
  • the light sources 216 may be positioned proximate a flexible substrate such as those described in U.S. Patent Publication No. 2005/0116235 (Schultz et al), entitled ILLUMINATION ASSEMBLY.
  • the illumination light unit 210 can also include sides and ends (not shown) located along the outer boundary of the unit 210 that are preferably lined or otherwise provided with high reflectivity vertical walls to reduce light loss and improve recycling efficiency.
  • the same reflective material used for the reflective substrate 218 can be used to form these walls, or a different reflective material can be used.
  • the side walls are diffusely reflective.
  • the ends can also include other reflectors, e.g., turning mirrors, tilted mirror film, etc.
  • Light sources 216 can include any suitable light source or combination of sources, e.g., those light sources described in regard to light sources 124 of FIG. 1.
  • the illumination light unit 210 also includes the elongated reflecting cavity 212 that includes the curved reflector 214.
  • the curved reflector 214 is concave down facing the substrate 218.
  • the curved reflector 214 can take any suitable cross-sectional shape, e.g., cylindrical, spherical, rectangular, etc.
  • the curved reflector 214 includes an elliptical cross-section in a plane substantially orthogonal to the substrate 218. For example, in the embodiment illustrated in FIG.
  • the curved reflector 214 has an elliptical cross-section in the x-z plane.
  • an ellipse is defined as a closed geometric figure shaped like an elongated circle and symmetric about two axes of different lengths, i.e., the major and minor axes.
  • FIG. 3 illustrates a cross-section view of a curved reflector 314 that has an elliptical cross-section in the plane of the drawing.
  • FIG. 3 also includes the outline of an ellipse 302 superimposed on the curved reflector 314 for illustration purposes.
  • the ellipse 302 includes a major axis 350 and a minor axis 352.
  • the ellipse also includes a first focus 354 and a second focus 356.
  • a light source placed at the first focus 354 of the curved reflector 314 For a light source placed at the first focus 354 of the curved reflector 314, light from the source that is incident on the curved reflector 314 will be reflected through the second focus 356.
  • the reflecting cavity 212 is elongated along an axis that is coincident with the y-axis.
  • the reflecting cavity 212 can be thought of as being formed by projecting the elliptical cross-section of the curved reflector 214 along the y-axis.
  • the curved reflector 214 converges with the substrate 218 in a direction away from the output surface 220.
  • the output surface 220 can take any suitable shape. Further, the output surface 220 can be substantially orthogonal to the substrate 218; alternatively, the output surface 220 can be canted at an angle to the substrate 218.
  • the curved reflector 214 forms a first line focus 222 that, in the illustrated embodiment, is substantially parallel with the y-axis.
  • the first line focus 222 refers to the collection of first foci of the elliptical cross-sections of the curved reflector 214.
  • the reflecting cavity 212 also includes a second line focus 224 that refers to the collection of second foci of the elliptical cross-sections of the curved reflector 214.
  • the light sources 216 are positioned proximate the first line focus 222.
  • the output surface 220 of the reflecting cavity 212 is positioned proximate the second line focus 224. Because the input surface 232 of the light guide 230 is positioned proximate the output surface 220 of the reflecting cavity 212, the input surface 232 is also positioned proximate the second line focus 224.
  • the curved reflector 214 may be any suitable type of reflector, for example a metalized reflector, or a multilayer dielectric reflector, which includes polymer multilayer optical film (MOF) reflectors.
  • the reflector 214 may include ESR.
  • the reflecting cavity 212 can include a solid optical body having a surface 214 that totally internally reflects at least a portion of light from the light sources 216.
  • the curved reflector 214 may be positioned such that the major axis of the ellipse formed in part by the curved reflector 214 is parallel to the substrate 218. In other embodiments, the major axis may be positioned at an angle to the substrate 218 such that the curved reflector's second line focus 224 is proximate a central region of the input surface 232 of the light guide 230.
  • the curved reflector 214 and the substrate 218 form a space 226.
  • the space 226 may be filled or may be empty. In embodiments where the space 226 is filled, for example, with a transparent optical body, then the reflector 214 may be attached to the outer surface of the body.
  • the space 226 can be filled using any suitable transparent material or materials, e.g., glass; acrylates, including polymethylmethacrylate, polystyrene, fluoropolymers; polyesters including polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and copolymers containing PET or PEN or both; polyolefms including polyethylene, polypropylene, polynorborene, polyolefins in isotactic, atactic, and syndiotactic sterioisomers, and polyolefins produced by metallocene polymerization.
  • suitable polymers include polyetheretherketones and polyetherimides. Different configurations of reflective cavities are described further in U.S. Patent No. 7,070,301 (Magarill).
  • At least a portion of illumination light from a light source 216 is emitted generally along the illumination axis 217 toward the reflector 214. Because the light source 216 is positioned proximate the first line focus 222 of the reflector 214, a portion of the illumination light is reflected by the reflector 214 toward the second line focus 224.
  • the input surface 232 of the light guide 230 which is positioned proximate the second line focus 224 of the reflector 214, receives the reflected light.
  • the light guide 230 can include extraction features (e.g., extraction features 132 of FIG. 1) that redirect the light from the illumination light unit 210 out of the light guide 230.
  • the reflecting cavity 212 allows the illumination light to expand in a direction substantially parallel with the y-axis of FIGS. 2A-B, thereby providing mixing of the various wavelengths of light.
  • illumination light within the reflecting cavity 212 is generally constrained in the x-z plane and allowed to expand in the x-y plane, and, therefore, various wavelengths of light can be mixed to provide white light to the light guide 230.
  • light sources 216 may include a first light source capable of producing illumination light at a first wavelength, and a second light source capable of producing light at a second wavelength different from the first wavelength.
  • the first wavelength may be in the blue region
  • the second wavelength may be in the yellow region. The blue and yellow light can then be mixed within the reflecting cavity 212 to provide white light to the light guide 230.
  • the light sources 216 can include a third light source capable of producing illumination light at a third wavelength different from the first and second wavelengths.
  • the first wavelength can be in the red region, the second wavelength in the green region, and the third wavelength in the blue region.
  • the red, green, and blue light can then be mixed within the reflecting cavity 212 to provide white light to the light guide 230.
  • Any number of different wavelength-emitting light sources can be provided in reflecting cavity 212.
  • the output surface 220 of the illumination light unit 210 is positioned proximate the input surface 232 of the light guide 230.
  • the unit 210 and the light guide 230 may be a unitary whole such that the output surface 220 and the input surface 232 are the same surface.
  • one or more optical elements can be positioned between the output surface 220 and the input surface 232.
  • the one or more optical elements can include any suitable optical element or elements, e.g., optical coupling agents such as adhesives or index matching fluids or gels, optical brightness enhancing films such as BEF (available from 3M Company), and short-wavelength absorbing materials such as ultraviolet light absorbing dyes and pigments, reflective polarizing films such as DBEF (also available from 3M Company), diffusers, lenses, controlled transmission films, and combinations thereof. See, e.g., U.S. Patent Application Publication No. 2006/0291238 (Epstein et al.).
  • the light guide 230 can include any suitable light guide, e.g., hollow or solid light guide. Although the light guide 230 is illustrated as being planar in shape, the light guide 230 may take any suitable shape, e.g., wedge, cylindrical, planar, conical, complex molded shapes, etc. Further, the light guide 230 can include any suitable material or materials.
  • the light guide 230 may include glass; acrylates, including polymethylmethacrylate, polystyrene, fluoropolymers; polyesters including polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and copolymers containing PET or PEN or both; polyolef ⁇ ns including polyethylene, polypropylene, polynorborene, polyolefms in isotactic, atactic, and syndiotactic sterioisomers, and polyolef ⁇ ns produced by metallocene polymerization.
  • Other suitable polymers include polyetheretherketones and polyetherimides.
  • the light guide 230 may be made of the same materials as are used for the illumination light unit 210. In other embodiments, the light guide 230 may be hollow.
  • FIG. 4 illustrates another embodiment of a backlight 400.
  • the backlight 400 includes a light guide 430 that includes a first input surface 432, and an illumination light unit 410 that includes an output surface 420 positioned proximate the input surface 432 of the light guide 430. All of the design possibilities and considerations in regard to the light guide 230 and the illumination light unit 210 of the embodiment illustrated in FIGS. 2A-B apply equally to the light guide 430 and illumination light unit 410 of the embodiment illustrated in FIG. 4.
  • the illumination light unit 410 of backlight 400 is similar in may regards to the unit 210 of backlight 200 of FIG. 2.
  • the unit 410 includes a substrate 418, and one or more light sources 416 positioned proximate the substrate 418. Each light source 416 is capable of generating illumination light generally along an illumination axis 417 that is substantially orthogonal to the substrate 418.
  • the unit 410 also includes an elongated reflecting cavity 412 that includes a curved reflector 414 that is concave down facing the substrate 418.
  • the curved reflector 414 includes an elliptical cross- section in a plane substantially orthogonal to the substrate 418 (e.g., in FIG. 4, the x-z plane).
  • the light sources 416 are positioned proximate a first line focus 454 of the reflecting cavity 412, and the output surface 420 of the cavity 412 is positioned proximate a second line focus 456 of the cavity 412.
  • the reflecting cavity 412 includes at least one facet 424 positioned between the light sources 416 and the output surface 420 of the reflecting cavity 412.
  • the facet 424 may be formed of any suitable reflective material or materials, e.g., metal, polymeric, etc.
  • facet 424 may include a polymeric multilayer optical film, e.g., ESR.
  • the reflecting cavity 412 can include a solid optical body having the facet 424 formed therein.
  • a facet 424 can be shaped so that it provides a surface that reflects incident light.
  • the facet 424 may be formed in the reflecting cavity, on the substrate, attached to the substrate, etc.
  • the facet 424 can include any suitable shape or shapes such that incident light is directed toward the output surface 420. Although the embodiment illustrated in FIG. 4 has only one facet, two or more facets may be included two direct incident light as described herein.
  • the elliptical curved reflector 414 is tilted at an angle to the input surface 432 of the light guide 430 such that the second line focus 456 is positioned proximate a central region of the input surface 432.
  • a major axis 458 of the elliptical curved reflector 414 is not orthogonal to the input surface 432 of the light guide 430.
  • the major axis 458 can be tilted at any suitable angle to the input surface 432 of the light guide 430.
  • FIG. 5 illustrates another embodiment of a backlight 500.
  • the backlight 500 includes a light guide 530 that includes a first input surface 532, a first illumination light unit 510 having the output surface 520 positioned proximate an input surface 532 of the light guide 530, and a second illumination light unit 540 having an output surface 550 positioned proximate the input surface 532. All of the design considerations and possibilities regarding the light guide 230 and the illumination light unit 210 of the embodiment illustrated in FIGS. 2A-B apply equally to the light guide 530, the first illumination light unit 510, and the second illumination light unit 540 of the embodiment illustrated in FIG. 5.
  • the first unit 510 and second unit 540 are positioned proximate the same input surface 532 of the light guide 530. As illustrated in FIG. 5, the second unit 540 is rotated in relation to the first unit 510 such that electrical connections to light sources 546 can more easily be provided.
  • the second unit 540 can be positioned in any suitable orientation or relationship to the first unit 510 such that both the first unit 510 and the second unit 540 are positioned proximate the same input surface 532 of the light guide 530.
  • the backlight 500 can include one or more additional illumination light units positioned along other edges of the light guide 530.
  • backlight 200 of FIGS. 2A-B can be manufactured by first providing light sources 216 on substrate 218.
  • the reflecting cavity 212 can then be formed on the substrate 218 using any suitable technique.
  • a solid reflecting cavity 212 can be formed onto the light sources 216 and substrate 218, e.g., by molding, such that the light sources are encased within the reflecting cavity 212.
  • Such a configuration can provide protection for the light sources 216 as the reflecting cavity 212 in essence encapsulates the light sources 216.
  • the illumination light unit 210 can then be positioned proximate the input surface 232 of the light guide 230 using any suitable technique.
  • the unit 210 can be attached to the input surface 232, held in place next to or in contact with the input surface 232, etc.
  • the unit 210 can be attached to the input surface 232 using a suitable adhesive, e.g., Norland OP29, OP21, OP40, or Summers SK9.
  • the reflecting cavity 212 and light guide 230 can be a unitary piece that is molded onto the light sources 216 and substrate 218.
  • the curved reflector 214 can then be positioned on or adjacent the reflecting cavity
  • a metal coating can be applied to or deposited onto the outer surface of the reflecting cavity 212.
  • the curved reflector 214 includes a polymeric multilayer optical film, then such film can be attached to the reflective cavity 212 using any suitable technique, e.g., attached using an optical adhesive.
  • the reflecting cavity 212 is hollow (i.e., space 226 is not filled using a liquid or solid material), then the curved reflector 214 can be positioned proximate the light sources 216 and light guide 230 using any suitable technique.
  • one end of the curved reflector 214 can be attached to or otherwise held in place on the substrate 218, and another end of the curved reflector 214 can be attached to or otherwise held in place on or adjacent the input surface 232 of the light guide 230.
  • the curved reflector 214 includes a polymeric multilayer optical film, e.g., ESR
  • the film can be formed using any suitable technique into the desired cross-sectional shape, e.g., thermoforming. Suitable techniques for forming polymeric multilayer optical films are further described, e.g., in U.S. Patent No. 6,788,463 (Merrill et al), entitled POST-FORMABLE MULTILAYER OPTICAL FILMS AND METHODS OF FORMING.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Planar Illumination Modules (AREA)

Abstract

L'invention concerne une unité d'éclairage (210) qui comporte un substrat (218), et au moins une première source de lumière (216) placée à proxumité du substrat (218). Ladite première source de lumière (216) peut produire une lumière d'éclairage généralement le long d'un axe d'éclairage (217) sensiblement orthogonal au substrat (218). L'unité de lumière d'éclairage (210) comporte également une cavité réfléchissante (212) allongée comportant un réflecteur incurvé (214) qui est concave par rapport au substrat (218). Le réflecteur incurvé (214) comporte une section transversale élliptique dans un plan sensiblement orthogonal au substrat (218). La première source de lumière (216) est placée à proximité d'une première focalisation linéaire (222) de la cavité réfléchissante (212) et une surface de sortie (220) de la cavité réfléchissante (212) est placée à proximité d'une seconde focalisation linéaire (224) de ladite cavité réfléchissante (212).
PCT/US2007/088270 2006-12-29 2007-12-20 Unité de lumière d'éclairage et afficheur l'utilisant WO2008083018A1 (fr)

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EP2138874A1 (fr) * 2007-09-13 2009-12-30 Kun Dian Photoelectric Enterprise Co. Fixation d'éclairage Del
DE102011055429A1 (de) * 2011-11-17 2013-05-23 Hella Kgaa Hueck & Co. Beleuchtungsvorrichtung für Fahrzeuge
WO2013075368A1 (fr) * 2011-11-23 2013-05-30 深圳市华星光电技术有限公司 Module de rétroéclairage et écran à cristaux liquides
FR3009065A1 (fr) * 2013-07-29 2015-01-30 Valeo Vision Dispositif optique de vehicule automobile
US9007547B2 (en) 2011-11-23 2015-04-14 Shenzhen China Star Optoelectronics Technology Co., Ltd. Backlight module and LCD device
US9341887B2 (en) 2009-09-11 2016-05-17 Dolby Laboratories Licensing Corporation Displays with a backlight incorporating reflecting layer
WO2017151423A1 (fr) * 2016-03-03 2017-09-08 Microsoft Technology Licensing, Llc Illuminateur en panneau plat à concentrateur

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WO2002014796A1 (fr) * 2000-08-16 2002-02-21 Motorola, Inc. Systeme d'eclairage en arriere plan d'un affichage
US20060215387A1 (en) * 2005-03-25 2006-09-28 Harvatek Corporation Backlight module
JP2006269289A (ja) * 2005-03-24 2006-10-05 Seiko Instruments Inc 照明装置およびこれを用いた液晶表示装置
US20060290844A1 (en) * 2005-06-24 2006-12-28 Epstein Kenneth A Optical element for lateral light spreading in edge-lit displays and system using same

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Publication number Priority date Publication date Assignee Title
WO2002014796A1 (fr) * 2000-08-16 2002-02-21 Motorola, Inc. Systeme d'eclairage en arriere plan d'un affichage
JP2006269289A (ja) * 2005-03-24 2006-10-05 Seiko Instruments Inc 照明装置およびこれを用いた液晶表示装置
US20060215387A1 (en) * 2005-03-25 2006-09-28 Harvatek Corporation Backlight module
US20060290844A1 (en) * 2005-06-24 2006-12-28 Epstein Kenneth A Optical element for lateral light spreading in edge-lit displays and system using same

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2138874A1 (fr) * 2007-09-13 2009-12-30 Kun Dian Photoelectric Enterprise Co. Fixation d'éclairage Del
US9341887B2 (en) 2009-09-11 2016-05-17 Dolby Laboratories Licensing Corporation Displays with a backlight incorporating reflecting layer
DE102011055429A1 (de) * 2011-11-17 2013-05-23 Hella Kgaa Hueck & Co. Beleuchtungsvorrichtung für Fahrzeuge
DE102011055429B4 (de) * 2011-11-17 2021-03-11 HELLA GmbH & Co. KGaA Beleuchtungsvorrichtung für Fahrzeuge
WO2013075368A1 (fr) * 2011-11-23 2013-05-30 深圳市华星光电技术有限公司 Module de rétroéclairage et écran à cristaux liquides
US9007547B2 (en) 2011-11-23 2015-04-14 Shenzhen China Star Optoelectronics Technology Co., Ltd. Backlight module and LCD device
FR3009065A1 (fr) * 2013-07-29 2015-01-30 Valeo Vision Dispositif optique de vehicule automobile
WO2017151423A1 (fr) * 2016-03-03 2017-09-08 Microsoft Technology Licensing, Llc Illuminateur en panneau plat à concentrateur
US9903995B2 (en) 2016-03-03 2018-02-27 Microsoft Technology Licensing, Llc Flat panel illuminator with concentrator
CN108780242A (zh) * 2016-03-03 2018-11-09 微软技术许可有限责任公司 带有聚光器的平板照明器
CN108780242B (zh) * 2016-03-03 2021-07-06 微软技术许可有限责任公司 带有聚光器的平板照明器

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